Method of treating sulphur



Jan. 17, I928. 1,656 504 I J. w. SCHWAB METHOD OF TREATING SULPHUR Original Filed Jan. 30. 1924 COLOR NUMBER Fl LTRATE. N 4- 0 IO 20 60 40 5O 60 70 80 90 PER CENT AD ORBENT PER CENT OIL IN FILTRATE o 0 IO 7O 8O PER CENT ADSORBENT INVENTOR #15 flaw/ W ATTORNEYS Patented Jan. 17, 1928.

tested UNITED STATES JAMES W. SCHWAB, OF GULF, TEXAS, ASSIGNOR TO TEXAS GULF SULPHUR COMPANY, OF BAY CITY, TEXAS, A CORPORATION OF TEXAS,

PATENT OFFICE.

METHOD OF TREATING SULPHUR.

Original application filed january 80, 1924, Serial No. 689,564. Divided and. this application filed.

December 10, 1926.

This invention relates to the treatment of sulphur, and more particularly to the treatment of sulphur containing impurities, such as small amounts of organic impurities, the presence of which impart to the sulphur an abnormal color or other objectionable property. The invention has for its object the provision of an improved method of treating such sulphur to improve its color and to ameliorate its other objec- 'tionable properties.

This application is a division of my copending application Serial No. 689,564, for

the method of treating sulphur.

w Sulphur is commonly produced or mined by underground fusion in accordance with the well-known Frasch process. In this process a fusing fluid, such as superheated water under pressure, is conveyed to the ml underground sulphur deposit where its heat is utilized in fusing the sulphur and the fused or melted sulphur is collected in the so-called sulphur wells and raised to the surface of the ground in a molten condition by suitable agencies, such, for example, as an air lift pump. The .molten sulphur is then permitted to solidify and forms what is known in the industry as crude sulphur.

Crude sulphur as mined by the Frasch process is more nearly a pure substance than many carefully purified chemically pure chemicals. It often assays 99.95% sulphur and averages well over 99.5% sulphur. But crude sulphur always contains, in addition to minute amounts of inorganic matter, traces of impurities which affect its burning qualities and sometimes its color. These latter impurities are largely organic matter and are present in the sulphur on account of its contact with petroleum or bituminous substances which occur in the sulphur-bearing formations. The organic impurities are usually referred to as oil.

Ordinary crude sulphur generally assays from 0.01% to 0.05% oil, but frequently contains larger amounts of oil. There does not seem to be any direct relationship between the amount of oil present in the sulphur' and its color. Sulphur containing 0.02% oil may be dark brown in color, while other sulphur containing as much as 0.07% to 0.08% oil may be a bright yellow color.

Serial No. 154,036.

Oil and sulphur react very rapidly at the temperatures prevailing at the burning point of sulphur itself and form black, asphaltic compounds which discolor the sulphur making it nearly black, and when burned an asphaltic fihn forms on the surface of the sulphur which ultimately extinguishes the flame. I have found that oil and sulphur react very slowly at the temperatures ordinarily prevailing in mining operations. If, however, crude sulphur is held for some time at the temperatures prevailing in mining operations, it loses its normal bright yellow color and becomes darker yellow or brownish in color. So, in actual mining, if sulphur as it is melted in the deposit does not happen to drain readily to a producing'well, it may remain in the liquid state long enough for some of the oil to react with it and cause it to lose its characteristic bright yellow color and become dark. And, should the temperature of the molten sulphur become abnormally high so that the sulphur becomes viscous, then the color of the sulphur becomes dark more rapidly. The particular shade (that is color) of the solid sulphur probably depends upon how long ithad remained in the liquid state before it finally reached a producing well and was removed from the deposit and solidified, and perhaps also, to some extent, upon the temperature attained by the sulphur while molten.

While the color of crude sulphur can be fairly well controlled by careful placing of producing wells with reference to the portion of the sulphur deposit bein mined, still there are often wells that pro uce dark or abnormally colored sulphur. In ordi nary mining practice, it seems impossible not to produce some sulphur which in chemical composition and properties is practically identical with bright yellow sulphur, but which is dark or abnormal in color. The color of this dark sulphur leads those accustomed to bright sulphur .to assume that it is inferior in quality and is, therefore, a drawback to the sale of a product which is equal in quality to bright yellow sulphur.

The present invention contemplates the provision of a method of treating dark or abnormally colored sulphur to improve its color and more particularly to restore dark sulphur to its normal and characteristic bright yellow color. The invention also contem lates the provision of an improved separating the sulphur from the adsorbent material and such adsorbed or occluded impurities as have become associated therewith. Thus, the invention involves bring I ing dark colored sulphur, in a molten or a the characteristic bright yellow an liquid condition, into intimate contact with artificial silicious substances, such for 1nstance, as silica gel, capable of adsorbing or occluding a large proportion of the oil and im rov ng to some extent the color of the sul ur. After a varying period .of contact, o from a few minutes to several hours, the sulphur is separated from the adsorptive substance and its adsorbed or occluded impurities by any ap ropriate means. The product is sulphur o a better color which contains noticeably lessoil than before treatmen't. o

I wish it to be understood that I do not intend to impl that the beneficial action of these artificia silicious materials is due solely to adsorption. .On the contrary, it is my present belief that occlusion or absorption may and probably does take place, although to' what extent the beneficial action of these materials is due, if at all, to these or other phenomena I am not now prepared to say.

I have found that silica gel possesses, to a marked extent, the properties desirable for the practice of the present invention, and under proper conditions this substance eliminates a large proportion of the oil in the sulphur and to some extent improves the color of the sulphur. The molten or li uid sulphur may 'be brought into the desired intimate contact with the silica gel in any convenient manner, such, for example, as by agitation with the silica gel,'or by filtration through a medium composed of or appropriate] containing the silica gel.

T e amount of adsorbent silica gel required in the practice of my invention varies with diiferent materials and with the amount of dark colored impurities and oil to be eliminated from the sulphur. Inthe case of silica gel less than 5% by weight on the amount of sulphur treated is usually suificient to restore the color of the sul hur to to remove a large percentage of the oil. In case it is desired to remove substantially all of the oil from the sulphur, larger percentages of silica gel may be required.

The temperature at which the sulphur and the adsorbent silica gel material are brought into contact may vary within wide linuts. From an operatlon standpoint, it is prefermolten sulphur through a be able to bring about this contact at tem ratures ordinarily now used in handlin l1 uid sul hur, that is, from 240 to 320 t is to be understood, however, that higher temperatures, or even lower temperatures, may if desired, be employed in the practice of the present invention.

The time of contact required for improving the color of sulphur and for the removal of the impurities therefrom varies with the particular substance used, with the percentage of the substance used, and with its degree of-comminution. With finely divided silica gel only a few minutes are re uired to get effective results. With less fine y divided silica gel much longer periods of contact maybe required. The time of contact required will also vary with the character of the sulphur treated and with the degree to which it is desired to carry decolorization and oil removal.

The manner in which the necessary contact between the liquid sulphur and the substance used for removing the impurities is brought about may vary according to conditions. In most cases I prefer either to -ercolate the of the adsorbent material, or to agitate the molten sulphur with the adsorbent material and afterwards remove the latter by any suitable means such as by settling and decanting,

filtering, centrifuging, or the like.

The activity of the adsorbent material is reduced by continued use in accordance with the invention by taking up a substantial amount of sulphur and impurities. In some cases the adsorbent material may be effectively reactivated or revivified and used again. Silica gel may be thus reactivated by heating to 800-1200 F. in the presence of air, and may then be reused in. the practice of the invention. While it seems probable that after each such reactivation there is a loss in eiiiciency, my investigations indicate that it is possible to reuse silica gel at least five to ten times and possibl more. The adsorbent material may also reactivated by dissolving the adsorbed or, occluded organic matter and sulphur in a suitable solvent, such, for example, as 'carbon bisulfide or carbon tetrachloride.

The invention will be further illustrated by the following example Ewample N 0. 1.

Agitation with adsorbent substance followed by filtration.

50 grams of very dark sulphur (6) assaying 0.08% oil were agitated with 3% by weight of 200 mesh silica gel for about five minutes at a temperature of about 260 F. The resulting mixture was filtered through filter paper. The sulphur filtrate was very bright in color (1) and assayed less than 0.01% oil.

notasoa.

- exception that the period of agitation was ill ill

hill

' longer.

Filtered product Percent silica gel 'ljime ll-mated Percent Color oil No.

Crude sulphur 0. 044 9 l 0. 009 2 0. 006 2 0. 003 I 2 Silica gel in the form of granules is not so efiective as when used as a powder. The smaller the granules the more effective the material becomes as an adsorbent agent. W hen silica gel is used in the form of granules the granules are not agitated with the melted sulphur but the granules are used as a filter bed. lln practice it has been found advantageous to use granular silica gel of from thirty to sixty mesh. Material of a liner mesh than sixty slows up the rate of percolation to such an extentthat its use is uneconomical, while the use of coarser mate rial necessitates the use of an abnormally thiclr filter bed or gives poor adsorptive results.

There being no standard method of determining the gradations of discoloration of sulphur an arbitrary system has been devised and standardized. Long familiarity with these samples enables one to accurately gauge the color of a sample without even a check comparison with the standards maintained for that purpose.

The standards as far as it is possible to describe the colors are as follows:

Color No.

Ordinary description Very, very bright. I Vcg'y bright.

Very dark.

ll rom color No. 8 on to lilo. 10 the shades are proportionately darker.

The action of the silica gel adsorbent is graphically illustrated in Figs. 1 and 2 of the accompanying drawings:

Fig. 1 re resents the plotted line of a dark colored su phur with a color number 10 which is treated with various amounts of the adsorbent reagent.

Fig. 2 represents graphically by a plotted line the presence of oil which is removed by varying amounts of the adsorbent reagent.

Both of the drawings show that percentages of adsorbents below 5% remove most of the color and oil while the remaining traces of oil and color are only removed by a large excess of the adsorbent reagent.

Throughout the preceding description,

particular stress has been laid on the applihll tained substantially equal to those obtained by the usual method of subliming. Silica gel appears to have a preferential action in the adsorption reaction, that is, the silica. gel seems to iclr up the oil more readily than it does t eimpurity which causes the darkening of the sulphur that is the reaction product between oil and sulphur. Thus, it may be found advantageous to use mixtures of silica gel with other adsorbents depending upon the silica gel to remove a preponderance of the oil present and depending upon one of the other preferential adsorbents to remove the dark colored reaction product. Thus, by using such a combination, sulphur may be substantially freed from oil and by the same process have its color considerably brightened.

ll claim:

1. The method of improving the color of abnormally colored sulphur which comprises treating the sulphur in a molten condition with timely divided silica gel, and separating the molten sulphur from the silica gel and thereby obtaining sulphur of a color substantially approximating the characteristic normal yellow color.

2. The method of improving the color of abnormally colored sulphur which comprises passing the sulphur in a molten condition through an appropriate bed containing silica gel whereby the molten sulphur is brought into intimate contact with the silica gel and the sulphur after passing there'through is more nearly of the characteristic yellow color of normal colored sulphur.

3. The method of treating sulphur con taining impurities, such as small amounts of organic matter, which impart to the sulphur... an abnormal color, which comprises bringing the sulphur in a molten condition into lllll) intimate contact with silica gel, and separating the sulphur while molten in the presence of finely divided silica gel, and separating the molten sulphur 'from the silica gel and thereby obtaining sulphur of a color substantially approximating the characteristic normal yellow color.-

5. The method of treating sulphur containing impurities, such as small amounts of organic matter, which impart to the sulphur an abnormal color, which comprises passing the sulphur while molten through a medium containing finely divided. silica gel and thereby substantially improving the color of the sulphur and removing from the sulphur a substantial portion of the impurities.

6. The method of treating sulphur con taining impurities, such as small amounts of organic matter, which impart to thesulphur an abnormal color, which comprises bringing silica gel into intimate contact with the sulphur at a temperature from about 240 F. to about 320 F., and separating the molten sulphur from the silica gel and thereby obtaining' sulphur of a color substantially a iproximating the characteristic normal ye low color. I

7. The method of treating sulphur containing contaminating constituents,'such as small amounts of organic impurities, which impart to the sulphur an a normal color, which comprises bringing silica gel which has been previously subjected to a temperature of about 800 F. to about 1200 F. in the presence of air into intimate contact with the sulphur while molten, andseparat-ing the molten sulphur from the silica gel and thereby obtaining sulphur of a color substantially approximating the characteristic normal yellow color.

8. The method of improving sulphur con taining contaminating im urities, which comprises bringing the sulp ur in a molten condition into contact with silica gel, and subsequently separatng the molten sulphur from the silica gel and the impurities associated therewith.

9. The method of treating sulphur con taining contaminating impurities which comprises passing the sulphur in a molten condition through a medium containing silica gel and thereby removing a large part of tllllf contaminating impurities from the sulabnormall v colored sulphur which comprises treating t e sulphur in a molten condition with artificial silicious adsorbent material, and separating the molten sulphur from the adsorbent material and thereby obtaining sulphur of a color substantially approximating the characteristic normal yellow color.

11. The method of treating sulphur containing impurities, such as small amounts of orgamcmzittenwhich impart to the sulphur an abnormal color, which comprises bringing an artificial silicious adsorbent material into intimate contact with the sulphur at a temperature from about 240 F. to about 320 F., and separating the molten sul hur from the adsorbent material and there y obtaining sulphur of a color substantially approximating the characteristic normal ,yellow color. 1 r

12. The method of treating sulphur containing contaminating im urities, which comprises "bringing the sulp ur in a molten condition into contact with an artificial silicious adsorbent material, and subs uently separating the molten sulphur from t e sili- 10. The method of improving thecolor of V cious adsorbent material and the impurities associated therewith.

In testimony whereof I afiix my signature.

JAMES w. SCHWAB. 

